Originally Posted by ghoffman

The engine pulled the Yak around great, but honestly the EF Extra is a much better plane.

Thanks for the feedback. So which of the two VVRC 40cc Twins fits in the EF 78" Extra?

Since I know one gent with the engine, and another 2 that has the 78, I will ask them both and report back.

Originally Posted by ghoffman

Since I know one gent with the engine, and another 2 that has the 78, I will ask them both and report back.

Sounds great! I appreciate it!

Originally Posted by RC_Feen

Thanks for the feedback. So which of the two VVRC 40cc Twins fits in the EF 78" Extra?

It has been posted the 1/4 32 plug fits quite well with room to spare. I do not think anyone has tried the other version on that plane. It seems the angled CM-6 plug is a relatively new change to this engine and very few have been shipped. The original CM-6 plug was straight off the head and not angled. The width was much wider. I would guess it was over 9".

On that note, I just ordered engine with the standard NGK CM-6 plug a few minutes ago. I plan on posting an answer to that with photos as soon as I get it on the nose. I really don't care if I have to do a slight cut out for the plugs, though we shall see.

I got tired of waiting for the DA35. Given my luck, It will probably ship next week!I figured I would order an extra cowl and sell the twin if I want to change the engine out in the future. My guess unless I start having reliability issues, I will be very happy with this engine.

Thanks patroller!......sounds great and I look forward to see how the CM-6 angled version fits in the EF 78" Extra 300.

OK, we have 1/2 of the answer, here is the width of the 78 EF Extra cowl.

Well the other 1/2 of the question in answered right from VVRC website.

( This engine is also available with the angled NGK CM-6 spark plugs. The distance from cap to cap on the engine with the Angled CM-6 spark plugs is 8-1/2". )

So the angled CM-6 plug, cap to cap, is 8 1/2" and the EF Extra cowl looks to be 9 3/8".

That's a good thing right there.

There is some offset to the left, about 3/8 inch.

Originally Posted by ghoffman

OK, we have 1/2 of the answer, here is the width of the 78 EF Extra cowl.

Originally Posted by 2robinhood

Well the other 1/2 of the question in answered right from VVRC website.

( This engine is also available with the angled NGK CM-6 spark plugs. The distance from cap to cap on the engine with the Angled CM-6 spark plugs is 8-1/2". )

So the angled CM-6 plug, cap to cap, is 8 1/2" and the EF Extra cowl looks to be 9 3/8".

That's a good thing right there.

Awesome! Thanks guys!

The EF 78 cowl obviously tapers more narrow towards the front. I measure a little less than 8" just behind the opening for the prop and the thrust washer. To estimate clearance I cut a piece of scrap balsa that was 8-1/2" and used that to gauge how far forward towards the nose it would clear, I also guessed with the photo provided earlier that the caps on the plugs would be an inch or so below the centerline. It is really close to 8-1/2" where I am guessing the caps would sit inside the cowl.

I would put money on having to cut a small opening for the cowl with the CM-6 plugs.

Originally Posted by patroller

The EF 78 cowl obviously tapers more narrow towards the front. I measure a little less than 8" just behind the opening for the prop and the thrust washer. To estimate clearance I cut a piece of scrap balsa that was 8-1/2" and used that to gauge how far forward towards the nose it would clear, I also guessed with the photo provided earlier that the caps on the plugs would be an inch or so below the centerline. It is really close to 8-1/2" where I am guessing the caps would sit inside the cowl.

I would put money on having to cut a small opening for the cowl with the CM-6 plugs.

The caps sit 3-1/4 back from the front of the cowl and about an inch below centerline. You will need 8 inch clearance with the angled 1/4-32 plugs and 8-5/8 clearance with the angled CM6 plugs at that point to clear the side walls of the cowl. Go with the 1/4-32 plugs. Only downside is they cost a few bucks more to replace. Up side, the engine will fit into more airplanes.

It's probably answered somewhere already but - Is there any difference in performance between the CM6 version and the 1/4-32 version?

My friend Joe measured his CM-6 version, and he said 8 3/4 at the end of the caps.

Good info...I was going to exhange mine for the CM6 plug configuration....but not NOW!

What is the 1/4 spark plug. I know the NGK CM 6 can be bought at auto parts places and other places.